Method of heating getters in strip-shaped holders



Sept. 3, 1963 A. R. HOVINGH ET AL METHOD OF HEATING ,GETTERS IN STRIP-SHAPED HOLDERS Filed March 17, 1960 INVENTOR A.R. HOVINGH H.J.R. PERDIJK AGENT United States Patent 3,102,764 .METHOD OF HEATING GE'ITERS m STRIP-SHAPED HOLDERS Albertus Remko Hovingh and Hendrik Johannes Reinierus Perdijk, Eindhoven, Netherlands, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Mar. 17, 1960, Ser. No. 15,615 Claims priority, application Netherlands Apr. 2, 1959 3 Claims. (Cl. 316-25) This invention relates to a method of heating a gasabsorbing substance (getter) provided on a strip-shaped holder during the manufacture of an electric discharge tube, and to an electric discharge tube manufactured by this method. r

During or afterthe process of degassing the electrodes of an electric discharge tube, it is frequently desirable for a getter to be heated in the tube to a temperature of from 700 C. to 900 C. by means of a high-frequency fieldproduced outside of the tube, for example, in order that the getter material is gradually vaporized or, with a non-vaporizing getter, in order to ensure satisfactory activation and optimum gettering action of the getter.

When, in the conventional arrangement, use is made of a strip-shaped getter holder, the latter is arranged at right angles to the high-frequency field so that heating is substantially effected by the eddy currents produced in the holder.

This method has a limitation in that the temperature to which the container is heated is highly dependent upon the intensity of the high-frequency field. This is a disadvantage in large-scale manufacture since the intensity of the high-frequency. field must be continuously supervised, since it may vary, for example owing to supply voltage fluctuations.

This disadvantage is completely avoided if, in accordance with the invention, the strip-shaped holder comprises a strip made of amagnetic material the Curie point of which lies in the range between 700 C. and 900 C. and is arranged parallel to the electromagnetic lines of force of the high-frequency field, so that during heating the temperature of the container rises to the Curie point and then is maintained constant. Preferably, the container is made of nickel-plated iron the Curie point of which is slightly lower than approximately 780 C., which is the temperature for pureiron. By the use of suitable metal alloys this point may be set to another value.

The getter can be provided on the holder as a coating or can be pressed into at'least one recess of the strip.

The invention will now be described more fully with reference to a drawing which shows a discharge tube provided with such a getter holder While this is arranged in the high-frequency field.

In the FIGURE, reference numeral 1 denotes the tube envelope in which an electrode system 2 is provided. On the system 2 there is arranged a strip-shaped getter holder 3 provided with getter pellets 4 which are pressed in recesses in the thin strip 3. The strip 3 is arranged parallel the electromagnetic lines of force of a high-frequency coil 5, which extend parallel to the tube axis. The surface area of the strip is not of importance. its thickness, however, must be small, for example 0.1 mm. Alternatively, the high-frequency field may be produced at right angles to the tube axis, in which event the strip 3 must'likewise be arranged at right angles to the tube axis. The strip 3 preferably consists of iron having a Curie point of approximately 780 (3., a length of 2 cms. and a width of 5 mms. In order to prevent oxidation, use can be made of nickel-plated iron having a slightly lower Curie point.

Although the use of the Curie point for obtaining a certain temperature is not new, since it is already used in high-frequency cooking apparatus, the food to be prepared being disposed in a bowl or pan made from ferrites, the conditions are widely different from those occurring when heating a metal strip. The ferrites are not electrically conductive so that no eddy current can be produced in the bowl. For this reason, the above-mentioned principle cannot be employed when using a metal bowl or pan, since such an article, which is large in three dimensions, will invariably be heated substantially by the eddy currents and a constant temperature, which is independent of the strength of the high-frequency field through a large range, will not be obtained. In addition, cooking in such apparatus is based on the heat produced in the food itself due to eddy currents and dielectric losses sothat screening by a conductive envelope cancels the effect of such a furnace.

What is claimed is:

l. A method of heating a gas-absorbing substance in an 2. A method as claimed in claim 1 in which the holder is strip-shaped.

3. A method as claimed in claim 2 in which the holder is a nickel-plated iron strip.

References Cited in the file of this patent UNITED STATES PATENTS 2,180,714 McQuade Nov. 21, 1939 2,393,541 Kohler Jan. 22, 1946 2,474,335 Skellett June 28, 1949 2,673,784 Snyder Mar. 30, 1954 

1. A METHOD OF HEATING A GAS-ABSORBING SUBSTANCE IN AN ELECTRIC DISCHARGE TUBE COMPRISING THE STEPS OF DISPOSING THE GAS-ABSORBING SUBSTANCE IN A SUBSTANTIALLY FLAT HOLDER CONSTITUTED OF A FERROMAGNETIC MATERIAL THE CURIE POINT OF WHICH IS BETWEEN ABOUT 700*C. AND 900*C., AND SUBJECTING THE HOLDER TO A HIGH FREQUENCY ELECTROMAGNETIC FIELD, THE LINES OF FORCE OF WHICH ARE PARALLEL TO THE PLANE OF THE HOLDER WHILE IN THE TUBE WHEREBY THE HOLDER IS HEATED TO THE CURIE POINT OF THE MAGNETIC MATERIAL AND MAINTAINED SUBSTANTIALLY CONSTANT THEREAT. 